You mention using a "bos soundlink mini 2", by which I assume you mean the "bose soundlink mini 2", which is an external bluetooth speaker which I gather you are connecting by 8th-inch cable?
If that is the case: do either of these things happen if you just use the laptop's built-in speakers?

The suggestion you already received for Silenzio will likely solve your second problem, as this is common with bluetooth speakers which are designed to conserve power by not playing noise below a certain threshold (I.E. silence).

However, your first "crackling" issue could be something else, and I have experienced something along those lines.

The next time you experience the crackling, can you test by switching to the laptop's internal speakers, and see if it is still happening?

If it is, try plugging in some unpowered headphones or earbuds, and see if you are still getting the crackling.
Actually, try that either way, then go back to the Bose. Report what happened at each stage.

How bad is this crackling? Can you record an audio sample of several seconds of it, possibly contrasted with normal sounding speech? What synth are you using?

Luke